Total Solar Eclipse, Salem OR
Short of being an astronaut, I'd wager that witnessing a total solar eclipse provides the most spectacular display of nature a person can see. Pictures don't convey the experience of being there in person, but they do serve as a complement, revealing more subtle details that are hard to absorb in the moment. 

Above: Composite image of the corona with different exposures targeting different regions.

Left: Massive solar flares peaking out behind the moon. For comparison, I copied a picture of earth roughly to scale. The careful viewer will notice that it is many times smaller than these violent flaming outbursts from the sun. 

Bottom left: The "diamond ring" effect occurs just moments before or after the moon completely blocks the sun. 

Bottom right: The sun's corona in more detail, and the star Regulus. Fun side note: the scientific field with one of the coolest names, involving study of the sun's corona: magnetohydrodynamics.